Language model biasing modulation

ABSTRACT

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for modulating language model biasing. In some implementations, context data is received. A likely context associated with a user is determined based on at least a portion of the context data. One or more language model biasing parameters based at least on the likely context associated with the user is selected. A context confidence score associated with the likely context based on at least a portion of the context data is determined. One or more language model biasing parameters based at least on the context confidence score is adjusted. A baseline language model based at least on the one or more of the adjusted language model biasing parameters is biased. The baseline language model is provided for use by an automated speech recognizer (ASR).

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.15/263,714, filed on Sep. 13, 2016, which is a continuation of U.S.patent application Ser. No. 14/673,731, filed on Mar. 30, 2015, theentire contents of each are hereby incorporated by reference.

FIELD

The present specification relates to automated speech recognition (ASR).

BACKGROUND

Language models, which are components of systems such as automatedspeech recognition (ASR) systems, assign probabilities to sequences oftext. ASR systems transcribe utterances into a series of computerreadable sounds, which are then compared to a dictionary of words in agiven language. The relative probabilities associated with severalcandidate sequences of words can be used to help select the most likelytranscription of an utterance.

SUMMARY

In general, one innovative aspect of the subject matter described inthis specification can be embodied in processes that modulate the extentto which language models are biased based on context data that couldindicate whether a user remains associated with a specific context, orwhether the user has switched to a different context. Modulatinglanguage model biasing enables an ASR system to reduce transcriptionword error rates, for example when the ASR system has low confidencethat biasing associated with a particular context should be performed.

Language model biasing may be modulated using context data such as thetime interval between a user query and user response to a presentationof results to the query, gaze tracking data indicating how the userdirects attention to visual content, or data indicating that the userhas switched between applications. A context selector may initiallycalculate a likely context based on the received context data and selecta set of biasing parameters that are associated with the likely context.A biasing modulator may then calculate a context confidence score of thelikely context, which represents the likelihood that the user remainswithin associated with the likely context based on receiving additionalcontext data. The biasing modulator may determine, based on the contextconfidence score, that the likely context associated with the user haschanged, and in response, interpolate the selected biasing parametersbased on the additional context data. The language model biaser may thenuse the modulated language model parameters to bias the language model,which is provided to an automated speech recognition module fortranscribing subsequent speech input.

For situations in which the systems discussed here collect personalinformation about users, or may make use of personal information, theusers may be provided with an opportunity to control whether programs orfeatures collect personal information, e.g., information about a user'ssocial network, social actions or activities, profession, a user'spreferences, or a user's current location, or to control whether and/orhow to receive content from the content server that may be more relevantto the user. In addition, certain data may be anonymized in one or moreways before it is stored or used, so that personally identifiableinformation is removed. For example, a user's identity may be anonymizedso that no personally identifiable information can be determined for theuser, or a user's geographic location may be generalized where locationinformation is obtained, such as to a city, zip code, or state level, sothat a particular location of a user cannot be determined. Thus, theuser may have control over how information is collected about him or herand used by a content server.

Implementations may include one or more of the following features. Forexample, a computer-implemented method including receiving context data;determining a likely context associated with a user, based on at least aportion of the context data, selecting one or more language modelbiasing parameters based at least on the likely context associated withthe user; determining a context confidence score associated with thelikely context based on at least a portion of the context data, andadjusting one or more of the language model biasing parameters based atleast on the context confidence score. The method also includes biasinga baseline language model based at least on one or more of the adjustedlanguage model biasing parameters; and providing the biased languagemodel for use by an automated speech recognizer (ASR).

Other versions include corresponding systems, apparatus, and computerprograms, configured to perform the actions of the methods encoded oncomputer storage devices.

In some implementations, the context confidence score reflects alikelihood that the likely context remains associated with the user. Insome implementations, the context confidence score associated with thelikely content is determined further based at least on additionalcontext data indicating that the user has switched to a different likelycontext. In some implementations, the baseline language model indicatesscores associated with different n-gram sequences.

In some implementations, additional context data includes dataindicating that the user has switched between applications, dataindicating a time difference between a presentation of a search resultand a user response to the presentation of the search result, gazetracking data, or data indicating a user behavior in response to visiblecontent.

In some implementations, adjusting one or more of the language modelbiasing parameters may include: comparing the context confidence scoreassociated with the likely context to a threshold context confidencescore value; determining, based at least on comparing the contextconfidence score associated with the likely context to the thresholdcontext confidence score value, that the likely context data does notremain associated with the user; in response to determining that thelikely context data does not remain associated with the user,interpolating one or more selected language model biasing parametersbased on at least the likely context; and providing, for output to alanguage module biaser, one or more adjusted language model biasingparameters based on at least the likely context with decreased biasingweights.

In some implementations, interpolating one or more language modelbiasing parameters includes: reducing, by a first magnitude, based onadditional context data indicating a time difference between apresentation of a search result and a user response to the presentationof the search result; or reducing, by a second magnitude, based onadditional context data including gaze tracking data.

The details of one or more implementations are set forth in theaccompanying drawings and the description below. Other potentialfeatures and advantages will become apparent from the description, thedrawings, and the claims.

Other implementations of these aspects include corresponding systems,apparatus and computer programs, configured to perform the actions ofthe methods, encoded on computer storage devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates examples of the modulation of language model biasing.

FIG. 2 illustrates an example system that may be used to performlanguage model biasing modulation.

FIG. 3 illustrates an example process for generating a biased languagemodel.

FIG. 4 is a block diagram of computing devices on which the processesdescribed herein, or potions thereof, may be implemented.

In the drawings, like reference numbers represent corresponding partsthroughout.

DETAILED DESCRIPTION

FIG. 1 illustrates examples of the modulation of language model biasing.In this example, a user 102 a issues a voice query 110 a to a userdevice 120 a, which displays a user interface 130 a through anapplication on its screen. The user interface 130 a includes a searchbox 132 a, a content display 136 a, and a banner ad 134 a. The system100 uses a timestamp 140 a to track the time interval between a voicequery 110 a and user input on the user interface 130 a. More detailedexamples are provided in subsequent figures and the correspondingdescription.

The user device 120 a may be any type of computing device that includesa microphone, such as a smartphone, tablet computer, laptop computer ordesktop computer. The user interface 130 a may be displayed through anymobile or desktop operating system that allows a user to provide a userquery and displays visual content, e.g., search results, in response tothe user query.

As illustrated in FIG. 1, the user 102 a, 102 b, and 102 c maycorrespond to the same user across various timestamps 140 a, 140 b, and140 c/140 d respectively. The voice queries 110 a-d, user devices 120a-d, and user interfaces 130 a-d may also correspond to the same orsimilar components across the timestamps 140 a-140 d, respectively.

In the example shown in FIG. 1, the user 102 a may initially submit avoice query to find Italian restaurants nearby by issuing a voice query110 a that includes the terms “Italian restaurant” to a user device 120a. In response to the voice query 110 a, the user interface 130 adisplays a list of search results that reference nearby Italianrestaurants on the content display 136 a. The system 100 further obtainslanguage model biasing parameters including the names of the restaurantsdisplayed on the content display 136 a. The system 100 uses thetimestamp 140 a of the voice query 110 a to track the time intervalbetween the user's initial voice query 110 a and a user input inresponse to a presentation of search results from the voice query 110 a.

After the user 110 a provides the voice query 110 a, the user 102 b mayprovide a second voice query 110 b that includes the terms “bestcalzones.” The system 100 may determine that this second voice query 110b is within the likely context of the user's initial voice query 110 a,based on the short time interval between time point 140 a and 140 b,e.g., five seconds, and that the content associated with the voice query110 a is related to the content associated with the voice query 110 b,i.e., calzones are a type of Italian food. In response, the system 100may determine that the user remains within the same context as the voicequery 110 a and continue to bias the language model to display searchresults that reference calzones on the content display 136 b, includingfor instance, image search results that are images of calzones.

After, a user 102 c may provide a voice query 150 that is phoneticallytranscribed as “PE-EH-SA PA-AH-IE,” and which is associated with thecandidate transcriptions “pizza pie” and “piece of pie.” In FIG. 1, userinterfaces 130 c and 130 d represent alternative biasing actions takenby the system 100 in response to the voice query 150. For instance, thesystem 100 may determine the likely context associated with the userbased on the voice queries 110 a-110 b and input provided on userinterfaces 130 a-130 b from time periods 140 a-b. In the example shownin FIG. 1, the system 100 may determine whether the user 102 c remainswithin the context of Italian food based on the context data received bythe user devices 120 a-120 b between the time points 140 a-140 b.

In one example, the system 100 may determine that the user 102 c isstill within the likely context of Italian food based on the intervalbetween timestamps 140 a and 140 c being ten seconds long. In thisexample, the system 100 does not modulate language model biasing andcontinues to bias the language model based on the initial voice query110 a to transcribe that the voice query 150 as “pizza pie”.

In some implementations, the system 100 may use additional context dataprovided by the user such as data indicating the amount of scrolling onthe interfaces 130 a-130 b, or touch input provided on the contentdisplays 136 a-136 b to determine the likely context of the user 102 c.In these implementations, the system 100 may determine that the user isstill within the likely context based on data indicating positiveinteractions with the displayed search results. In response, the system100 may bias the language model to increase likelihoods of wordsassociated with Italian food, e.g., “pizza.”

In another example, the system 100 may determine that the user 102 c isnot within the likely context of Italian food. For instance, the system100 may calculate a context confidence score for biasing the languagemodel based on the initial voice query 110 a. The context confidencescore may represent the likelihood that the user 102 c is within thecontext associated with voice query 110 a when the user submits thevoice query 150. The system may use context data such as extended timeinterval between timestamps 140 a and 140 d, e.g., thirty seconds, tocalculate the confidence score based on a threshold time interval forresponse time. Based on determining that the interval between timestamps140 a and 140 d is above the threshold, the system 100 may calculate alow context confidence score for the likely context of Italian food,which indicates that the user 102 c is not within the likely context ofItalian food. In this example, the system 100 may attenuate or disablelanguage model biasing based on Italian food.

The system 100 interpolates the language model using modulated biasingparameters to transcribe the voice query 150 based on receiving contextdata indicating that the likely context content is no longer associatedwith the user 102 c. For example, the system 100 may use additionalcontext data 150 b in addition to the voice queries 110 a and 110 b todetermine whether the context associated with the user has changed sincesubmitting the initial voice query 110 a. For instance, such additionalcontext data may include gaze tracking data that reflects eye movementsfrom a front-side camera near the screen of the user device 120 a. Insuch instances, if the gaze tracking data indicates that the user 102 cspent more time looking at the banner ad 134 b than the content display136 b, the system 100 may determine that the content display 136 b doesnot confidently represent the likely context associated with the user.The system 100 may then attenuate or disable language model biasingbased on the context display 136 b to control the transcription of thevoice query 150. In other instances, the system 100 may use other typesof context data such as data indicating a touch input, time lapsebetween presentation of user content and the user response to thecontent, or switching between other applications on the user device 110a.

In other implementations, the system 100 may interpolate the languagemodel used to transcribe the voice query 150 by modulating a set ofbiasing language model parameters that indicate the likelihoods ofcertain words within the language model based on receiving additionalcontext data. For example, in response to determining that the timeinterval between the timestamps 140 a and 140 d is above a thresholdvalue, e.g., 15 seconds, and receiving data indicating that the user 102c selected the banner 134 b, the system 100 may reduce the biasing ofwords associated with Italian food within the language model to generatea biased language model. In this example, the system 100 may reduce thebiasing parameters related to Italian food using decay factors thatattenuate the associated likelihoods within the language model. Inanother example, the system 100 may determine that the additionalcontext data indicates a likely context so divergent from Italian food,that the system 100 may disable biasing based on Italian food. In thisexample, the system 100 generates replacement biasing parameters toprevent incorrect language model biasing based on an irrelevant usercontext.

FIG. 2 illustrates an example system that may be used to performlanguage model biasing modulation. Briefly, a context selector 220includes a biasing parameter selector 224 that selects biasingparameters 226 based on the received context data 222. The selectedbiasing parameters 228 are transmitted to a biasing modulator 230, whichincludes a context confidence estimator 234. The biasing modulator 230generates modulated biasing parameters 236 and may also receiveadditional context data 232. A language model biaser 240 selects abaseline language model 242 to bias based on the receiving the modulatedbiasing parameters 236. The language model biaser 240 then transmits abiased language model 254 to an automated speech recognition module 250.The acoustic model 252 uses the biased language model 254 to transcribesubsequent speech input provided by a user.

The context selector 220 includes a biasing parameter selector 224. Thecontext selector 220 may be a computer-implemented program thatprocesses user queries through voice queries. The user query includecontext data 222, which allows the context selector 220 to determine alikely context associated with the user based on the received userqueries. For example, the context data 222 may include number and typeof words used within the user query, or time lapses between signals,e.g., notifications on user interfaces, and user response. The likelycontext associated with the user may be a list of candidate topics thatare correlated with the information included within the user query.

The biasing parameter selector 224 may select a set biasing parametersfrom a repository of biasing parameters 226 based on the likely contextassociated with the user. For example, in response to a user query“Italian food near me”, the context selector 220 may determine that thelikely context may be restaurants or food within a certain distance,e.g., one mile radius, from the user's location. The system 200 generatea list of candidate restaurants in response to the query, and thebiasing parameter selector 224 may select the names of the restaurantsas the biasing parameters 226 for the user query. The context selector220 may then transmit the selected biasing parameters 228 to the biasingmodulator 230.

The biasing modulator receives the transmitted selected biasingparameters 228 and includes a context confidence estimator 234. Thebiasing modulator may also receive context data 222 associated with theuser query and additional context data 232 from subsequent user inputprovided after the initial user query. The context confidence estimator234 calculates a context confidence score, which indicates thelikelihood that the likelihood that the likely context remainsassociated with the user. For example, the user may provide an initialquery “Italian food near me” and then provide input indicating that theuser has switched between multiple applications over a certain timeperiod. In this example, the context confidence estimator may calculatea low context confidence score based on the additional context data 232related to the switching between multiple applications.

In some implementations, context confidence estimator 234 may calculatethe context confidence score based on an aggregation of multiple contextdata that positively indicate that the user remains associated with thelikely context or negatively indicate that the user has switched to adifferent likely context. Examples that positively indicate that theuser remains associated with the likely context may include dataindicating short time lapses between the user query and a user responseto a presentation of results to the query, subsequent queries related toor within the same category as the initial query, e.g., “Italian food”and “pizza”. Other examples that negatively indicate that the user hasswitched to a different likely context may include data indicating thatthe user has taken a longer time to provide a response to a presentationof results to a query, data indicating that the user has switched to adifferent topic or interest as suggested by interactions with otherapplications or resubmitting the initial query with minor changes,indicating that the user was not satisfied with the results of theinitial query. The context confidence estimator 234 may also calculatemagnitudes of multiple weight factors in determining the contextconfidence score based on the specific context data. For example, thecontext confidence estimator 234 may prioritize different context datasignals and determine the appropriate magnitudes to up weight or downweight the context data based on prior data indicating successfulqueries and unsuccessful queries.

The biasing modulator 234 interpolates the selected biasing parameters228 transmitted from the context selector 220 based on the contextconfidence score associated with the likely context. For example, thebiasing modulator 234 may compare the context confidence scoreassociated with the likely context to a threshold context confidencescore value. The biasing modulator 234 may determine, based on comparingthe context confidence score associated with the likely context to thethreshold context confidence score value, that the likely context doesnot remain associated with the user. In response to determining that thelikely context data does not remain associated with the user, thebiasing modular may interpolate the selected language model biasingparameters. For example, the biasing modulator may add decay factors tothe selected biasing parameters 228 to decrease the associatedprobabilities of the parameters or reduce the weights of the biasingparameters in the language model. In some instances, the contextconfidence score may be so low, that the biasing modulator 230 maytransmit a signal to the biasing parameter selector to select a new setof biasing parameters based on the additional context data 232 received.In other instances, biasing modulator 230 may attenuate theprobabilities of the selected biasing parameters 228 to generate andtransmit a set of modulated biasing parameters 236.

The language model biaser 140 receives the modulated biasing parameters136 to bias the baseline language model 142. The baseline language model242 is a set of assigned probabilities to a sequence of n-grams by usinga probability distribution. The baseline language model 242 may also bea unigram model, or a positional language model that describes thepossibility of given words occurring close to one another within a text.The language model biaser 140 biases the baseline language model 142 byadjusting probabilities associated with words within the language modelthat increase the chances of being responsive to the user query. Forexample, the language model biaser 140 may use the modulated biasingparameters to identify certain words or terms that indicate that a useris within a certain context based on the context data associated withthe user query. The language model biaser 240 generates a biasedlanguage model, which is transmitted to the automatic speech recognitionmodule 250.

The automated speech recognition module 250 receives the biased languagemodel 254 and includes an acoustic model 252. The acoustic model 252identifies a transcription of speech input provided by a user into areadable text. The automatic speech recognition module 250 uses thebiased language model 254 to recognize the transcription by the acousticmodel 252 and reduce the word error rate predicting the transcription isan accurate representation of the speech input.

FIG. 3 illustrates an example process 300 for generating a biasedlanguage model. Briefly, the system 300 receives context data (310). Thesystem 200 determines a likely context associated with a user based onthe context data (320). The system 200 selects language model biasingparameters based on the likely context (330). The system 200 determinesa context confidence score associated with the likely context based onthe context data (340). The system 200 adjusts the language modelbiasing parameters based on the context confidence score (350). Thesystem 200 biases a baseline language model based on the adjustedlanguage model biasing parameters (360). The system 200 provides thebiased language model for use by an automated speech recognizer (370).

The system 300 receives context data (310). For example, the system 200may receive a user request through a verbal utterance indicating asearch query for locations nearby the user. The system 200 maytranscribe the utterance using an automated speech recognition modulewithin the user device. For instance, the user may say “Italianrestaurants near me” and the system 200 may use the transcribed words touse a discriminative technique to determine the user context. In thisexample, the system 200 may determine that the user is searching forfood based on the transcription of word “restaurant” and determine thatthe user is searching for specific types of food based on the word“Italian” to describe a specified cuisine.

The system 200 determines a likely context associated with a user basedon the context data (320). For example, based on the received user querydescribed in process step 310, the context selector 220 may determinethat the likely context associated with the user is a list of Italianrestaurants within a mile of the location of the user device. In thisexample, the system 200 may determine the likely context by combiningthe terms within the user query based on a baseline language model thathas a predetermined probabilities associated with combinations of words.

The system 200 selects language model biasing parameters based on thelikely context (330). For example, the biasing parameter selector 224may select a set of biasing parameters 226 based on the determinedlikely context. For instance, in the example described in process step320, the biasing parameter selector 224 may select the names of thelisted restaurants that are identified as likely context for the userquery. The biasing parameter selector 224 determines these biasingparameters based on their association with user query “Italianrestaurants near me”.

The system 300 determines a context confidence score associated with thelikely context based on the context data (340). For example, the contextconfidence estimator 234 may determine the context confidence score thatis indicative of the likelihood of each likely context remainsassociated with the user. The context confidence estimator 234 may usedata indicating user behavior to calculate the context confidence score.For example, the context confidence estimator may use the number oftimes the user has switches between different applications, scrollingdata after providing a query, or the time difference between the userquery and a user selection to determine if the context associated withthe user has changed. If the data indicating user behavior has changedfrom the likely context, e.g., resubmitting a query, failing to send aresponse within a threshold time period, switching between a thresholdnumber of applications, the context confidence estimator 234 assigns alow context confidence score to the likely context. If the dataindicating user behavior is within the likely context, or has notchanged from the likely context, the context confidence estimator 234assigns a high context confidence score to the likely context.

In some implementations, the context confidence estimator 234 maydetermine the context confidence score of the likely context based oncomparing the selected biasing parameters to verify user query. Forexample, if a user submits the query “vanilla car,” the biasingparameter selector 224 may select a list of biasing parameters relatedto ice cream based on biasing around the transcription “vanilla” andbiasing parameters related to transportation based on biasing around thetranscription “car”. In such an instance, the context confidenceestimator 234 may determine that the context confidence score for thelikely context is low based on determining that ice cream andtransportation are unlikely to represent actual user context.

The system 200 adjusts the language model biasing parameters based onthe context confidence score (350). For example, the biasing modulator230 may receive additional context data 232 to attenuate the selectedbiasing parameters 228 and generate a set of modulated biasingparameters 236. The biasing modulator 230 may use the additional contextdata to determine if the user is still within the likely context. In Insuch examples, the additional context data 232 may include time intervalbetween a user query and user response to a presentation of results,gaze tracking data indicating where the user directs his/her attentionon visual content, data indicating that the user has switched betweenapplications, user input indicating that the user has selected one ofthe presented results, the user has submitted a new search query thatindicates that the user has tried to retry the search query withdifferent terms, or combinations of these examples.

In some implementations, adjusting the language model biasing parametersinitially includes comparing the context confidence score associatedwith the likely context to a threshold context confidence score value.The biasing modulator 230 may determine, based on comparing the contextconfidence score associated with the likely context to the thresholdcontext confidence score value, that the likely context does not remainassociated with the user. For example, if the context confidenceestimator 234 determines that the selected biasing parameters indicate alow confidence score based on the combination of transcriptions from theuser query, the biasing modulator 230 may determine that this below thethreshold value and that the user does not remain associated with theuser. In response to determining that the likely context data does notremain associated with the user, the biasing modulator 230 mayinterpolate the selected biasing parameters 228 based on the likelycontext. For example, if a user provides a search query “vanilla car”and the biasing parameter selector 224 may initially select biasingparameters related to ice cream and transportation. The user may thenprovide a subsequent search query “vanilla cone”, which the biasingmodulator 230 may use to determine that the selected biasing parametersrelated to transportation are no longer relevant based on the user'sresubmitted search query. In response, the biasing modulator 230 mayattenuate the likelihoods associated with these biasing parametersand/or increase the likelihoods associated with the biasing parametersrelated to ice cream.

In some implementations, the biasing modulator 234 interpolates theselected biasing parameters using decay factors based on type ofadditional context data received by the biasing modulator 232. Forinstance, the biasing modulator 232 may use additional context dataindicating the time interval between a user query and user response to apresentation of results to add a decay factor that reduces the biasingparameters proportionally with the increase in time interval. In anotherinstance, the biasing modulator 232 may use context data indicating thatthe user has switched applications to reduce the biasing parameters byadding decay factor that is certain percentage for each successiveapplication switch. In these examples, the biasing modulator 234interpolates the selected biasing parameters using specified decayfactors that are specific to the types of context data associated withthe user and may combine the decay factors with the selected biasingparameters using various algorithmic methods to reduce the associatedlikelihoods of the biasing parameters.

In other implementations, the biasing modulator 230 may use deactivationthresholds for different types of context data to remove selectedbiasing parameters altogether. For example, the biasing modulator mayset a deactivation threshold for time interval for a user response atone minute. In such an example, if the user take more than a minute toprovide a response to an initial query, then the biasing modulator 230discards the selected biasing parameters and interprets the response asinitiating a new search query. In response, the biasing parameterselector may select new biasing parameters that are more relevant to thesecond search query. In such examples, the deactivation thresholds mayvary based on the type of context data, and may interact with otherdeactivation thresholds of other context data to create an additive ormultiplicative impact on the biasing parameters. For instance, if thedeactivation thresholds for switching applications is four switches, andthe deactivation threshold for time interval is 30 seconds, the biasingmodulator 230 may remove the selected biasing parameters if the user hasspent 20 seconds and has switched between three applications.

The system 200 biases a baseline language model based on the adjustedlanguage model biasing parameters (360). For example, the biasingmodulator 230 provides a set of modulated biasing parameters 236 to thelanguage model biaser 240, which includes a baseline language model 242.In such examples, the modulated biasing parameters 236 are based on thelikely context associated with the user selected by the context selector220 and are modulated by the biasing modulator 230 based on the contextconfidence score calculated context confidence estimator 234. Themodulated biasing parameters 236 are used to control the biasing of thebaseline language model to enhance the responsiveness to a user query.

In one example, the modulated biasing parameters 236 are used by thelanguage model biaser 240 to positively bias the baseline language model242. For example, if a user provides a search query “Italian restaurantsnear me”, in response the system 200 may present a list of ten resultsincluding “John's pizzeria”, “Paolo Trattoria”. The context languagemodel biaser concurrently prepares a baseline language model 242, andthe biasing parameter selector selects biasing parameters based on therestaurant names of the displayed results. If the user provides a voicecommand stating “John's pizzeria” within a 30 second time interval, thenthe biasing modulator 230 determines, based on such additional contextdata, that the selected biasing parameters related to “John's pizzeria”have a relatively high context confidence score, and allows the languagemodel biaser 240 to bias the baseline language model 242 using thebiasing parameters based on the restaurant names of the displayedresults.

In another example, the modulated biasing parameters 236 are used by thelanguage model biaser 240 to negatively bias the baseline language model242. For example, in response to the list of restaurants discussedabove, the user may change applications on the user device, and providea subsequent response two minutes after being presented with the list ofrestaurants. In this example, the biasing modulator may determine, basedon the additional context data such as the response time and theapplication switching, that the context confidence score of the biasingparameters based on the restaurant names is low enough to suggest thatthe user is no longer within the context of the initial search query. Inresponse, the biasing modulator 230 may either deactivate biasing by thelanguage model biaser 240 based on the selected biasing parameters orprepare new set of biasing parameters based on the second search querysubmitted, or a combination of both.

The system 300 provides the biased language model for use by anautomated speech recognizer (370). For example, the language modelbiaser provides a biased language model 254, using the modulated biasingparameters 236 to bias a baseline language model 242, to an acousticmodel 252 within an automated speech recognition module 250. Forinstance, the biased language model 255 may include the baselinelanguage model with biasing components that provide indications whetherto bias phrases received by the acoustic model using the language model.The biasing components may represent probabilities/likelihoods, orweights associated with certain words or phrases based on the modulatedbiasing parameters 236.

In some implementations, the biased language model 254 includesattenuated probabilities for certain words or phrases within thebaseline language model 242 based on the likely user context determinedby the context selector 220, and modulated by the biasing modulator 230.For example, if a user submits an initial search query “Italianrestaurants”, and subsequently submits an ambiguous search query withthe utterances “PE-EH-SA PA-AH-IE”, the biasing modulator may attenuatecertain probabilities within the baseline language model 242 based onthe context data provided by the user. For instance, if the userprovides a quick response and selects an option for an Italianrestaurant, the biased language model may have increased probabilitiesfor words related to Italian food such as “pizza”. However, if the userprovides a slow response, and/or interacts with other applications orcontent, e.g., scrolling between the page, switching betweenapplications, the biased language may have decreased probabilities forwords related to Italian food based on a determination by the biasingmodulator 230 that the user is no longer within the context of Italianfood. In such an example, the utterance may transcribed by the acousticmodel 250 using the baseline language model, which may lead theautomated speech recognition 250 to transcribe the user's utterance as“piece of pie”.

FIG. 4 is a block diagram of computing devices that may be used toimplement the systems and methods described in this document, as eithera client or as a server o plurality of servers.

FIG. 4 is a block diagram of computing devices 400, 450 that may be usedto implement the systems and methods described in this document, aseither a client or as a server or plurality of servers. Computing device400 is intended to represent various forms of digital computers, such aslaptops, desktops, workstations, personal digital assistants, servers,blade servers, mainframes, and other appropriate computers. Computingdevice 450 is intended to represent various forms of mobile devices,such as personal digital assistants, cellular telephones, smartphones,and other similar computing devices. Additionally computing device 400or 450 can include Universal Serial Bus (USB) flash drives. The USBflash drives may store operating systems and other applications. The USBflash drives can include input/output components, such as a wirelesstransmitter or USB connector that may be inserted into a USB port ofanother computing device. The components shown here, their connectionsand relationships, and their functions, are meant to be exemplary only,and are not meant to limit implementations of the inventions describedand/or claimed in this document.

Computing device 400 includes a processor 402, memory 404, a storagedevice 406, a high-speed interface 408 connecting to memory 404 andhigh-speed expansion ports 410, and a low speed interface 412 connectingto low speed bus 414 and storage device 406. Each of the components 402,404, 406, 408, 410, and 412, are interconnected using various busses,and may be mounted on a common motherboard or in other manners asappropriate. The processor 402 can process instructions for executionwithin the computing device 400, including instructions stored in thememory 404 or on the storage device 406 to display graphical informationfor a GUI on an external input/output device, such as display 416coupled to high speed interface 408. In other implementations, multipleprocessors and/or multiple buses may be used, as appropriate, along withmultiple memories and types of memory. Also, multiple computing devices400 may be connected, with each device providing portions of thenecessary operations, e.g., as a server bank, a group of blade servers,or a multi-processor system.

The memory 404 stores information within the computing device 400. Inone implementation, the memory 404 is a volatile memory unit or units.In another implementation, the memory 404 is a non-volatile memory unitor units. The memory 404 may also be another form of computer-readablemedium, such as a magnetic or optical disk.

The storage device 406 is capable of providing mass storage for thecomputing device 400. In one implementation, the storage device 406 maybe or contain a computer-readable medium, such as a floppy disk device,a hard disk device, an optical disk device, or a tape device, a flashmemory or other similar solid state memory device, or an array ofdevices, including devices in a storage area network or otherconfigurations. A computer program product can be tangibly embodied inan information carrier. The computer program product may also containinstructions that, when executed, perform one or more methods, such asthose described above. The information carrier is a computer- ormachine-readable medium, such as the memory 404, the storage device 406,or memory on processor 402.

The high speed controller 408 manages bandwidth-intensive operations forthe computing device 400, while the low speed controller 412 manageslower bandwidth intensive operations. Such allocation of functions isexemplary only. In one implementation, the high-speed controller 408 iscoupled to memory 404, display 416, e.g., through a graphics processoror accelerator, and to high-speed expansion ports 410, which may acceptvarious expansion cards (not shown). In the implementation, low-speedcontroller 412 is coupled to storage device 406 and low-speed expansionport 414. The low-speed expansion port, which may include variouscommunication ports, e.g., USB, Bluetooth, Ethernet, wireless Ethernetmay be coupled to one or more input/output devices, such as a keyboard,a pointing device, microphone/speaker pair, a scanner, or a networkingdevice such as a switch or router, e.g., through a network adapter. Thecomputing device 400 may be implemented in a number of different forms,as shown in the figure. For example, it may be implemented as a standardserver 420, or multiple times in a group of such servers. It may also beimplemented as part of a rack server system 424. In addition, it may beimplemented in a personal computer such as a laptop computer 422.Alternatively, components from computing device 400 may be combined withother components in a mobile device (not shown), such as device 450.Each of such devices may contain one or more of computing device 400,450, and an entire system may be made up of multiple computing devices400, 450 communicating with each other.

The computing device 400 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as astandard server 420, or multiple times in a group of such servers. Itmay also be implemented as part of a rack server system 424. Inaddition, it may be implemented in a personal computer such as a laptopcomputer 422. Alternatively, components from computing device 400 may becombined with other components in a mobile device (not shown), such asdevice 450. Each of such devices may contain one or more of computingdevice 400, 450, and an entire system may be made up of multiplecomputing devices 400, 450 communicating with each other.

Computing device 450 includes a processor 452, memory 464, and aninput/output device such as a display 454, a communication interface466, and a transceiver 468, among other components. The device 450 mayalso be provided with a storage device, such as a microdrive or otherdevice, to provide additional storage. Each of the components 450, 452,464, 454, 466, and 468, are interconnected using various buses, andseveral of the components may be mounted on a common motherboard or inother manners as appropriate.

The processor 452 can execute instructions within the computing device450, including instructions stored in the memory 464. The processor maybe implemented as a chipset of chips that include separate and multipleanalog and digital processors. Additionally, the processor may beimplemented using any of a number of architectures. For example, theprocessor 410 may be a CISC (Complex Instruction Set Computers)processor, a RISC (Reduced Instruction Set Computer) processor, or aMISC (Minimal Instruction Set Computer) processor. The processor mayprovide, for example, for coordination of the other components of thedevice 450, such as control of user interfaces, applications run bydevice 450, and wireless communication by device 450.

Processor 452 may communicate with a user through control interface 458and display interface 456 coupled to a display 454. The display 454 maybe, for example, a TFT (Thin-Film-Transistor Liquid Crystal Display)display or an OLED (Organic Light Emitting Diode) display, or otherappropriate display technology. The display interface 456 may compriseappropriate circuitry for driving the display 454 to present graphicaland other information to a user. The control interface 458 may receivecommands from a user and convert them for submission to the processor452. In addition, an external interface 462 may be provide incommunication with processor 452, so as to enable near areacommunication of device 450 with other devices. External interface 462may provide, for example, for wired communication in someimplementations, or for wireless communication in other implementations,and multiple interfaces may also be used.

The memory 464 stores information within the computing device 450. Thememory 464 can be implemented as one or more of a computer-readablemedium or media, a volatile memory unit or units, or a non-volatilememory unit or units. Expansion memory 474 may also be provided andconnected to device 450 through expansion interface 472, which mayinclude, for example, a SIMM (Single In Line Memory Module) cardinterface. Such expansion memory 474 may provide extra storage space fordevice 450, or may also store applications or other information fordevice 450. Specifically, expansion memory 474 may include instructionsto carry out or supplement the processes described above, and mayinclude secure information also. Thus, for example, expansion memory 474may be provide as a security module for device 450, and may beprogrammed with instructions that permit secure use of device 450. Inaddition, secure applications may be provided via the SIMM cards, alongwith additional information, such as placing identifying information onthe SIMM card in a non-hackable manner.

The memory may include, for example, flash memory and/or NVRAM memory,as discussed below. In one implementation, a computer program product istangibly embodied in an information carrier. The computer programproduct contains instructions that, when executed, perform one or moremethods, such as those described above. The information carrier is acomputer- or machine-readable medium, such as the memory 464, expansionmemory 474, or memory on processor 452 that may be received, forexample, over transceiver 468 or external interface 462.

Device 450 may communicate wirelessly through communication interface466, which may include digital signal processing circuitry wherenecessary. Communication interface 466 may provide for communicationsunder various modes or protocols, such as GSM voice calls, SMS, EMS, orMMS messaging, CDMA, TDMA, PDC, WCDMA, CDMA2000, or GPRS, among others.Such communication may occur, for example, through radio-frequencytransceiver 468. In addition, short-range communication may occur, suchas using a Bluetooth, WiFi, or other such transceiver (not shown). Inaddition, GPS (Global Positioning System) receiver module 470 mayprovide additional navigation- and location-related wireless data todevice 450, which may be used as appropriate by applications running ondevice 450.

Device 450 may also communicate audibly using audio codec 460, which mayreceive spoken information from a user and convert it to usable digitalinformation. Audio codec 460 may likewise generate audible sound for auser, such as through a speaker, e.g., in a handset of device 450. Suchsound may include sound from voice telephone calls, may include recordedsound, e.g., voice messages, music files, etc. and may also includesound generated by applications operating on device 450.

The computing device 450 may be implemented in a number of differentforms, as shown in the figure. For example, it may be implemented as acellular telephone 480. It may also be implemented as part of asmartphone 482, personal digital assistant, or other similar mobiledevice.

Various implementations of the systems and methods described here can berealized in digital electronic circuitry, integrated circuitry,specially designed ASICs (application specific integrated circuits),computer hardware, firmware, software, and/or combinations of suchimplementations. These various implementations can includeimplementation in one or more computer programs that are executableand/or interpretable on a programmable system including at least oneprogrammable processor, which may be special or general purpose, coupledto receive data and instructions from, and to transmit data andinstructions to, a storage system, at least one input device, and atleast one output device.

These computer programs (also known as programs, software, softwareapplications or code) include machine instructions for a programmableprocessor, and can be implemented in a high-level procedural and/orobject-oriented programming language, and/or in assembly/machinelanguage. As used herein, the terms “machine-readable medium”“computer-readable medium” refers to any computer program product,apparatus and/or device, e.g., magnetic discs, optical disks, memory,Programmable Logic Devices (PLDs), used to provide machine instructionsand/or data to a programmable processor, including a machine-readablemedium that receives machine instructions as a machine-readable signal.The term “machine-readable signal” refers to any signal used to providemachine instructions and/or data to a programmable processor.

To provide for interaction with a user, the systems and techniquesdescribed here can be implemented on a computer having a display device,e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitorfor displaying information to the user and a keyboard and a pointingdevice, e.g., a mouse or a trackball by which the user can provide inputto the computer. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback, e.g., visual feedback,auditory feedback, or tactile feedback; and input from the user can bereceived in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in acomputing system that includes a back end component, e.g., as a dataserver, or that includes a middleware component, e.g., an applicationserver, or that includes a front end component, e.g., a client computerhaving a graphical user interface or a Web browser through which a usercan interact with an implementation of the systems and techniquesdescribed here, or any combination of such back end, middleware, orfront end components. The components of the system can be interconnectedby any form or medium of digital data communication, e.g., acommunication network. Examples of communication networks include alocal area network (“LAN”), a wide area network (“WAN”), and theInternet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

A number of embodiments have been described. Nevertheless, it will beunderstood that various modifications may be made without departing fromthe spirit and scope of the invention. In addition, the logic flowsdepicted in the figures do not require the particular order shown, orsequential order, to achieve desirable results. In addition, other stepsmay be provided, or steps may be eliminated, from the described flows,and other components may be added to, or removed from, the describedsystems. Accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. A computer-implemented method comprising:receiving, by an automated speech recognizer (ASR) that is configured touse a language model that has previously been biased for use intranscribing utterances, audio data corresponding to an utterance;determining that, when the audio data was received, a particular contextthat is associated with biasing the language model is no longerapplicable; in response to determining that the particular context thatis associated with biasing the language mode is no longer applicablewhen the audio data was received, configuring the ASR to use an unbiasedlanguage model for use in transcribing utterances; after configuring theASR to use the unbiased language model for use in transcribingutterances, generating, by the ASR, a transcription of the utteranceusing the unbiased language model; and providing a representation of thetranscription for output.
 2. The method of claim 1, wherein configuringthe ASR to use the unbiased language model comprises returning thebiased language model to a baseline state, or reducing an effect of theprevious biasing of the language model.
 3. The method of claim 1,wherein determining that the particular context that is associated withbiasing the language model is no longer applicable comprises determiningthat a predetermined period of time has elapsed.
 4. The method of claim1, wherein determining that the particular context that is associatedwith biasing the language model is no longer applicable comprisesdetermining that a user that spoke the utterance is likely in adifferent context.
 5. The method of claim 1, wherein determining thatthe particular context that is associated with biasing the languagemodel is no longer applicable comprises determining that a confidencescore associated with the particular context does not satisfy athreshold.
 6. The method of claim 1, wherein determining that theparticular context that is associated with biasing the language model isno longer applicable comprises determining that a user that spoke theutterance is likely associated with another context that is inconsistentwith the particular context.
 7. The method of claim 1, whereinconfiguring the ASR to use the unbiased language model comprisesgenerating a modulated set of biasing parameters.
 8. A computer storagemedium storing instructions that, when executed by data processingapparatus, cause the one or more computers to perform operationscomprising: receiving, by an automated speech recognizer (ASR) that isconfigured to use a language model that has previously been biased foruse in transcribing utterances, audio data corresponding to anutterance; determining that, when the audio data was received, aparticular context that is associated with biasing the language model isno longer applicable; in response to determining that the particularcontext that is associated with biasing the language mode is no longerapplicable when the audio data was received, configuring the ASR to usean unbiased language model for use in transcribing utterances; afterconfiguring the ASR to use the unbiased language model for use intranscribing utterances, generating, by the ASR, a transcription of theutterance using the unbiased language model; and providing arepresentation of the transcription for output.
 9. The medium of claim8, wherein configuring the ASR to use the unbiased language modelcomprises returning the biased language model to a baseline state, orreducing an effect of the previous biasing of the language model. 10.The medium of claim 8, wherein determining that the particular contextthat is associated with biasing the language model is no longerapplicable comprises determining that a predetermined period of time haselapsed.
 11. The medium of claim 8, wherein determining that theparticular context that is associated with biasing the language model isno longer applicable comprises determining that a user that spoke theutterance is likely in a different context.
 12. The medium of claim 8,wherein determining that the particular context that is associated withbiasing the language model is no longer applicable comprises determiningthat a confidence score associated with the particular context does notsatisfy a threshold.
 13. The medium of claim 8, wherein determining thatthe particular context that is associated with biasing the languagemodel is no longer applicable comprises determining that a user thatspoke the utterance is likely associated with another context that isinconsistent with the particular context.
 14. The medium of claim 8,wherein configuring the ASR to use the unbiased language model comprisesgenerating a modulated set of biasing parameters.
 15. A systemcomprising: one or more computers including one or more storage devicesstoring instructions that when executed by the one or more computerscause the one or more computers to perform operations comprising:receiving, by an automated speech recognizer (ASR) that is configured touse a language model that has previously been biased for use intranscribing utterances, audio data corresponding to an utterance;determining that, when the audio data was received, a particular contextthat is associated with biasing the language model is no longerapplicable; in response to determining that the particular context thatis associated with biasing the language mode is no longer applicablewhen the audio data was received, configuring the ASR to use an unbiasedlanguage model for use in transcribing utterances; after configuring theASR to use the unbiased language model for use in transcribingutterances, generating, by the ASR, a transcription of the utteranceusing the unbiased language model; and providing a representation of thetranscription for output.
 16. The system of claim 15, whereinconfiguring the ASR to use the unbiased language model comprisesreturning the biased language model to a baseline state, or reducing aneffect of the previous biasing of the language model.
 17. The system ofclaim 15, wherein determining that the particular context that isassociated with biasing the language model is no longer applicablecomprises determining that a predetermined period of time has elapsed.18. The system of claim 15, wherein determining that the particularcontext that is associated with biasing the language model is no longerapplicable comprises determining that a user that spoke the utterance islikely in a different context.
 19. The system of claim 15, whereindetermining that the particular context that is associated with biasingthe language model is no longer applicable comprises determining that aconfidence score associated with the particular context does not satisfya threshold.
 20. The system of claim 15, wherein determining that theparticular context that is associated with biasing the language model isno longer applicable comprises determining that a user that spoke theutterance is likely associated with another context that is inconsistentwith the particular context.